1. Field of the Invention
This invention relates to rotary drums for treating materials; and, more particularly, to rotary drums having unitary material treating members forming a portion of the drum shell wall.
2. Description of the Prior Art
Rotary drums are used in a variety of industrial processes for treating liquid, pulverous and granular materials. Rotary kilns, for example, provide a familiar example of the use of such drums.
Rotary drums typically comprise a plurality of joined ring-shaped sections including one or more sections having material treating members such as scoops, cooling pipe supports and aperture coamings, extending radially inwardly or outwardly to facilitate treating or advancing the material. The ring-shaped sections are typically made of rolled and welded steel plate, and there is relatively little difference between the sections containing the material treating members and the remaining sections, except that the former may be made of an increased thickness plate for greater strength and rigidity.
The material treating members do not form a part of the wall but rather are attached to an already formed wall. Typically, these members are made of steel plate parts welded to one another and to the shell plate. Alternatively, they may comprise castings welded to the internal or external surfaces of one or more of the shell plates.
There are serious problems associated with the manufacture and use of the material treating members of these drums. The welded treating members are very difficult to fabricate. They typically require very complex welding operations at locations which are nearly inaccessible, e.g., the space beneath and between the tubes of a planetary cooler. In addition, the welded seams in these treating members often produce undesirable shearing stresses and, as a result, a weakening of the welded joints.
Drums with cast treating members attached to the wall have also been difficult to fabricate. The abrupt changes in thickness at the juncture between the rolled shell plates and the cast members has required the use of very high preheating temperatures with the consequence that manual welding is impractical.